Apparatus for detecting infrared radiation

ABSTRACT

An apparatus for detecting radiation and a change in position of the radiation source movable along a path has a radiationsensitive electronic semiconductor. A bridge circuit having resistances is formed from the semiconductor and these resistances are grouped into two pairs of mutually adjacent resistances. Two of the resistances, one from each of the pairs, have respective elongated surface portions disposed one adjacent the other along a common line. The surface portions jointly cover the range over which the radiation source is movable. The apparatus is positionable to have the surfaces face the radiation so that the line is substantially parallel to the path over which the radiation source is movable.

United States Patent [191 Paul 1 Jan. 16, 1973 [5 APPARATUS FORDETECTING FOREIGN PATENTS OR APPLICATIONS INFRARED RADIATION 1,214,8074/1966 Germany ..317/235 0 [75] Inventor: Bernt Paul, Erlangen, GermanyOTHER PUBLICATIONS [73] Assignee: Siemens Aktiengesellschaft, Berlin,

' K RHEEIfiffiifij) Gardner, Semiconductor Temperature Sensor, IBMTechnical Disclosure Bulletin, Aug. 1965, pp. 458 & [22] Filed: Dec. 2,1970 Appl. No.: 94,295

Foreign Application Priority Data Dec. 9, 1969 Germany ..P 19 61 574.8

US. Cl ..250/210, 73/355 R, 250/833 H,

317/235 Q, 324/DIG. 1, 338/25 Int. Cl ..H0lj 39/12 Field of Search..250/83.3 H, 210; 317/235 Q, 317/235 H; 73/355 R; 324/65 B, 62 BPrimary Examiner-Stanley T. Krawczewicz Attorney-Curt M. Avery, ArthurE. Wilfond, Herbert L. Lerner and Daniel .1. Tick 1 57] ABSTRACT Anapparatus for detecting radiation and a change in position of theradiation source movable along a path has a radiation-sensitiveelectronic semiconductor. A bridge circuit having resistances is formedfrom the semiconductor and these resistances are grouped into two pairsof mutually adjacent resistances. Two of the resistances, one from eachof the pairs, have respective elongated surface portions disposed oneadjacent the other along a common line. The surface portions jointlycover the range over which the radiation source is movable. Theapparatus is positionable to have the surfaces face the radiation sothat the line is substantially parallel to the path over which theradiation source is movable.

8 Claims, 4 Drawing Figures APPARATUS FOR DETECTING INFRARED RADIATIONMy invention relates to an apparatus for detecting radiation preferablytemperature radiation, especially infrared radiation and for detecting achange of location of the radiation with a temperature sensitiveelectronic semiconductor element. Such thermal electronic positiondetectors are used to localize the location of objects with the aid ofthe radiation emitted from these objects. These detectors have achievedsignificance in medical diagnosis and research as well as fortemperature investigations in the chemical industry and also for loopcontrol in rolling mill works.

Morten and King have described an infrared position detector having aplurality of individual infrared detectors in Infrared Physics, 1968,vol. 8, pages 9 to 14. In this position detector, the infrared detectorsare disposed in a line mutually adjacent to each other. A great numberof such lines form the detector surface. The individual detectors arescanned with a frequency of about 250,000 image spots per second. Thesum of the individual detectors, for example 10,000 in number, can bescanned in l/25 seconds. This apparatus is therefore suitable forinfrared television transmission. However, this apparatus performs itsfunction with a relatively large technological effort and investment inelectronic parts. It further has the disadvantage that the resolvingpower in line direction is limited by the smallest possible separationof the individual detectors from each other, this amount beingapproximately 100 pm.

For different areas of application, for example, in infrared followercontrol systems or in loop control in wire and light-section rollingmills, there is simply required the registration of the positionaldeparture of the radiation in a linear dimension. An arrangement forsolving this task includes a rotating polygon mirror which reflects theimpinging radiation onto a radiation sensitive electronic component.Determined by the mechanical arrangement of the rotating polygon mirror,a concentrated scanning ray passes a given viewing region in unison withthe frequency determined by the number of turns and so directs aninfrared radiation entering the region onto the detector. By means ofeach polygon mirror, each spot of the viewing region is scannedapproximately 100 times per second. Should a gliding member of rollingmaterial be located in the viewing range, the radiation detector isilluminated as soon asthe scanning ray reaches the edge of thematerialbeing rolled. The impinging radiation produces an electricalimpulse that is converted and amplified, and via a full-wave rectifieris sent to, for example, the control electrode of a thyristor. Theradiation detector has a lead sulfide semiconductor body whosesensitivity region is known not to extend substantially beyond a wavelength of 3 pm. The area of application is thereby correspondinglylimited and in this connection, only radiators having a temperatureabove 200C can be detected. The polygon mirror of this arrangement mustbe very precisely adjusted. In addition, because of its mechanicallymoving parts, the arrangement has a limited life of operation andrequires a relatively large expense to maintain.

Accordingly, it is an object of my invention to provide an apparatus fordetecting infrared radiation of simpler construction and improvedreliability.

It is another object of my invention to provide an apparatus fordetecting radiation and a change in the position of the radiation sourcemovable along a path.

The invention is based on the concept that a known apparatus of aradiation detector with radiation sensitive resistances connected as abridge circuit is suitable for detecting location because this apparatusprovides a signal of opposite polarity when one of the adjacentresistances of the bridge circuit is irradiated.

According to a feature of the invention, a bridge circuit hasresistances formed from a radiation-sensitive semiconductor body ofwhich at least one of the adjacent resistances serves as radiationdetector. These resistances are grouped into two pairs of mutuallyadjacent resistances. Two of the resistances, one from each of thepairs, have respective elongated surface portions disposed one adjacentthe other along a com mon line. The surface portions jointly cover therange over which the radiation source is movable. The apparatus ispositionable to have the surfaces face the radiation so that the line issubstantially parallel to the path along which the radiation source ismovable.

In a preferred embodiment and according to another feature of theinvention, the resistances are grouped into two groups of mutuallyopposite resistances and the resistances of each of the groups are atleast approximately mutually parallel. The two groups are disposed oneadjacent the other along a common line substantially parallel to thepath along which the radiation source is movable. Y

The radiation-sensitive resistances of such photo (quantum process) orbolometer effect (thermal process) or a radiation detector based on botheffects are preferably configured in a bridge circuit. For temperaturecompensation, such a bridge must comprise resistances having atemperature depending that is as identical as possible. According to mycopending US. Pat. application, Ser. No. 20,213, filed Mar. 17, 1970 andassigned to the assignee of the instant application, this requirement isfulfilled by etching the entire bridge from a crystal of thesemiconductor material so that the bridge circuit is a monolithicentity.

The invention will now be described with reference to the accompanyingdrawing, wherein:

FIG. I is a schematic diagram showing the apparatus of the inventiontogether with a path over which the source of radiation can travel andthe transfer function or characteristic of the radiation detector of theapparatus;

FIG. 2 is a circuit diagram of the resistances comprising the positiondetector; and,

FIGS. 3 and 4 illustrate respective embodiments of the position detectorof the invention.

FIG. I shows a radiation source 2 which is preferably a temperatureradiator, especially an infrared radiator. Radiation source 2 is shownat the B position and is movable through the center position to the Aposition. The radiation from radiator 2 is directed to a bridge detector8 via an objective 6 of the bridge detector 8. Only a base plate 10 andthe radiation sensitive resistances l 1, 12, 13 and 14 are shown.

Should the radiation source 2 move from the center position to the endposition A, the radiation impinging on the detector 8 will move from thecenter position of the resistances 11 to 14 in a direction to the outerend of resistances 12 and 14. In a similar manner, the impingingradiation will move from the center position between the resistances 11to 14 in a direction to the outer end of resistances 11 and 13 when theradiation source moves from the center position in the oppositedirection toward the end position B. Since many different kinds ofradiation sources can be considered, the radiation source is simplyrepresented by a base 4 which defines the range over which the radiationsource is movable with respect to the detector.

Referring still to FIG. 1, beneath the bridge detector 8, the detectorcharacteristic shows the output signal U, of the detector in dependenceupon the distance of the impinging radiation from the midpoint of thebridge. Should the impinging radiation move toward the right from thecenter portion of the resistance arrangement, the impinging radiationirradiates the two resistances 12 and 14 and the bridge circuit providesa positive signal at its output as soon as the spot covered by theimpinging radiation is detected by the two left ends of the resistances.The output signal is reduced somewhat from its maximum value just beforethe location X, as soon as a portion of the impinging beam moves outpast the end of the two resistances 12 and 14. The bridge circuitprovides an output signal of opposite sign in the same manner as soon asthe radiation source 2 moves from its center position in a direction ofposition B and, correspondingly, the impinging radiation moves along tothe outer end of the resistances 11 and 13 corresponding to point X onthe characteristic. In this way, at least an approximate antisymmetricalsensitivity characteristic and the output signal of the bridge circuitforms therefor a measure or index of the location of the radiationsource 2.

According to the circuit diagram of FIG. 2, the radiation sensitiveresistances 11 to 14 are connected to an input voltage U which, forexample, can be an alternating current voltage. The input voltage U isconnected across the input terminals 16 and 17. The output signal U, canbe taken from the output terminals 18 and 19.

' If only one of the two mutually adjacent resistances is radiated forexample resistance 11, its resistance value R, increases to an amount RAR. If the resistance values of all resistances when not beingirradiated are assumed to have all the same value R, an output signal isobtained with the increased resistance R AR given by: v

lnstead'of'the above, if two opposite lying branches, for example, theresistances 11 and 13 are irradiated, the resistance value of theresistance 13 will also increase in value in correspondence with theincreasein value of resistance 11 to an amount R AR. In this instance,an output signal is obtained given by rangement can be raised by afactor of two.

For the objective 6 in FIG. 1, a lens objective or mirror objective canbe used.

In the embodiment of the radiation detecting apparatus according to FIG.3, the resistances 11 to 14 are formed from a crystal of thesemiconductor material of a first crystalline phase preferably of indiumantimonide with inclusions of a second crystalline phase. The inclusionscomprise a material of good electrical conductivity such as nickelantimonide (NiSb), the electrical conductivity of the latter beinghigher than the electrical conductivity of the first phase material.Preferably, the resistances 11 to 14 are formed from the crystal ofsemiconductor material by etching. The mutually opposite resistances ll,13 and the mutually opposite resistances 12, 14 are mutually parallel,respectively. These two pair of parallel resistances are elongated andextend along a common line substantially parallel to the path over whichthe radiation source is movable and so are located to detect thepossible departure of the latter from a central reference position. Toemphasize the functioning resistance regions of the semiconductor body,these portions are designated in FIGS. 3 and 4 by hatching. Theinterconnects 21, 22, 23 and 24 do not introduce significant re-'sistance because of their considerably large cross-section. If desired,the resistance value of these connecting leads can be further reducedadvantageously by providing a good electrically conducting layer,preferably, the layer can be of aluminum, gold or silver. This layer canbe applied to the upper surface of the semiconductor body with theexception of the resistance region. The layer is preferably applied bymeans of a vapor deposition. The interconnects of the resistances areconnected to input terminals 16 and 17 by connecting leads 26 and 27,respectively, and to output terminals 18 and 19 via connecting leads 28and 29, respectively. The input and output terminals are dimensioned aspass through pins which extend through correspondingbores in the baseplate 10 and are electrically isolated with respect thereto. I

A modified transistor holder can for example be used as a base plate 10.To isolate these pins from the base plate 10, glass linings 31 can beused. Beneath the resistances 11 to 14 there is provided a groove 33 inthe base plate 10 of the bridge detector. The groove can for example bemilled into the base plate 10. The resistances l l to 14 extendunsupported over this groove. In this way, the heat conducted away fromthe resistances is reduced and the sensitivity of the apparatus iscorrespondingly increased.

According to FIG. 4 respective connecting leads can be provided for allresistances ll to 14 of the bridge circuit between these resistances andthe input terminals and output terminals. The connecting leads betweenthe input terminal 16, 17 and resistances 11, 12 and 13, 14,respectively, are designated42 and 43. The connecting leads of theoutput terminals 18 and 19 with the resistances 12, 13 and 11, 14 aredesignated with 45 and 44, respectively. In each instance, an end of theresistances 11 to 14 has a solder connection. For this purpose each endof a resistance is broadened to a sufficiently large surface whereas thewidth of the resistance itself is generally not greater than 1 mm,preferably, only less than 1 10 of a mm. The ends of the resistances aredetermined by means of cross-sectional widenings in combination withvaporization. With a length of the resistances of, for example, severalmillimeters, there is obtained a total length of a resistance pair ofapproximately 12 to 20 mm. This corresponds to approximately theelongation of the entire arrangement. In this way the smallest possiblespacing of the parallel resistances 11 and 13 or 12 and 14, which doesnot substantially exceed in general 1/10 of a millimeter, is held overthe entire length.

If the entire resistance arrangement is formed from a commonsemiconductor crystal, preferably by etching, and the resistancearrangement is subsequently secured to a base plate so that theresistances 11 to 14 are arranged free carrying or unsupported over thegroove 33, then the joining portions shown by dashed lines in FIG. 4between the resistances 11, 14 and 12, 13 are removed by means ofrespective borings 47 and 48 or by corresponding milling actions. In thesimilar or same manner, the joinings at the outer ends of theresistances 11, 13 and 12, 14 are removed, preferably by mechanicalseparation.

In the event that the apparatus of the instant invention should beprovided for determining the position of radiation of higher temperatureexclusively, especially temperatures over 200 C, resistances 11 to 14,for example, can be selected having a semiconductor body made of leadsulfide (PbS). Such radiation sensitive semiconductor elements have theadvantage of a relatively small time constant.

Should it also be desired to determine the position of radiation oflower temperature, it is preferable that the resistances be selectedwith a semiconductor body of a first crystalline phase having inclusionsof a second crystalline phase. The inclusions should be of a materialhaving a good electrical conductivity and this conductivity should behigher than that of the first phase crystalline body. For example, sucha configuration is taught in German Pat. No. 1,214,807 wherein asemiconductor body of indium antimonide (lnSb) with inclusions of nickelantimonide (NiSb) is disclosed.

According to US. Pat. No. 3,442,823 compounds of type CB" are suitablefor inclusions with A" 'B" semiconductor in which the C is an elementfrom the group Fe, Co, Ni, Cr, and Mn, and B is an element of Group V ofthe Periodic Table of Elements. Suitable inclusions can, for example,consist of FeSb, FeAs, CoAs, CrSb and CrAs as well as MnSb. In addition,vanadiumgallium V Ga or gallium-vanadium-antimonide GaV Sb can be used.A thermoelectronic position detector with such resistances can be usedto determine the direction of radiation having a temperature down toabout 40C.

With regard to the manufacture and application of a semiconductor whosecrystalline body is not crystallographically homogeneous but contains,integrally imbedded in the semiconductor substance proper, a multitudeof electrically or magnetically different inclusions mutually spaced andgenerally aligned to form a spacial matrix within the crystal, referencemay be had to US. Pat. No. 3,226,225.

For manufacturing the apparatus according to the invention everybolometer material having a low specific resistivity is suitable.

While the invention has been described by means of a specific exampleand in a s ecific embodiment} do no wish to be imlted there 0, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

lclaim:

1. Apparatus for detecting radiation and a change in position of aradiation source, said apparatus comprising a monolithic crystalsemiconductor body having two pairs of radiation-sensitive resistancesformed therein and connected in opposition in a bridge circuit, at leasttwo of the opposing resistances functioning as radiation receivers, andbeing positioned in parallel and closely adjacent each other in thedirection of movement of the radiation source, each of the resistanceshaving receiving surfaces which extend in the direction of displacementof the radiation source, the resistances being stationary in positionrelative to radiation from the radiation source, the resistances havinga central point therebetween, and said bridge circuit having outputmeans producing an output signal which is directly proportional to thedeviation of impinging radiation from the central point, said outputsignal having a polarity which is dependent upon the direction of thedeviation.

2. Apparatus according to claim 1, said resistances being grouped in twogroups of mutually opposite resistances, the resistances of each of saidgroups being at least substantially parallel, said two groups beingdisposed closely adjacent each other along a common line.

3. Apparatus according to claim 1, said resistances being formed from asemiconductor of a first crystalline phase, said semiconductor beingmade of a A'" B"- semiconductor material having inclusions of a secondcrystalline phase, said inclusions having an electrical conductivityhigher than said first phase.

4. Apparatus according to claim 1, said resistances being formed from asemiconductor body of lead sulfide (PbS).

5. Apparatus according to claim 1, further comprising a base platehaving a groove, said resistances being disposed on said plate andextending unsupported over said groove.

6. Apparatus according to claim 1, further comprising connectingportions for respectively connecting said resistances to form saidbridge circuit, said resistances and said connecting portions beingformed from a monolithic crystal of the semiconductor.

7. Apparatus according to claim 1, further comprising a metal layer onsaid semiconductor, said metal layer having openings at said resistancesto permit radiation to impinge upon the latter.

8. Apparatus according to claim 6, further comprising a metal layer onsaid semiconductor, said metal layer having openings at said resistancesto permit radiation to impinge upon the latter.

1. Apparatus for detecting radiation and a change in position of aradiation source, said apparatus comprising a monolithic crystalsemiconductor body having two pairs of radiationsensitive resistancesformed therein and connected in opposition in a bridge circuit, at leasttwo of the opposing resistances functioning as radiation receivers, andbeing positioned in parallel and closely adjacent each other in thedirection of movement of the radiation source, each of the resistanceshaving receiving surfaces which extend in the direction of displacementof the radiation source, the resistances being stationary in positionrelative to radiation from the radiation source, the resistances havinga central point therebetween, and said bridge circuit having outputmeans producing aN output signal which is directly proportional to thedeviation of impinging radiation from the central point, said outputsignal having a polarity which is dependent upon the direction of thedeviation.
 2. Apparatus according to claim 1, said resistances beinggrouped in two groups of mutually opposite resistances, the resistancesof each of said groups being at least substantially parallel, said twogroups being disposed closely adjacent each other along a common line.3. Apparatus according to claim 1, said resistances being formed from asemiconductor of a first crystalline phase, said semiconductor beingmade of a AIII BV- semiconductor material having inclusions of a secondcrystalline phase, said inclusions having an electrical conductivityhigher than said first phase.
 4. Apparatus according to claim 1, saidresistances being formed from a semiconductor body of lead sulfide(PbS).
 5. Apparatus according to claim 1, further comprising a baseplate having a groove, said resistances being disposed on said plate andextending unsupported over said groove.
 6. Apparatus according to claim1, further comprising connecting portions for respectively connectingsaid resistances to form said bridge circuit, said resistances and saidconnecting portions being formed from a monolithic crystal of thesemiconductor.
 7. Apparatus according to claim 1, further comprising ametal layer on said semiconductor, said metal layer having openings atsaid resistances to permit radiation to impinge upon the latter. 8.Apparatus according to claim 6, further comprising a metal layer on saidsemiconductor, said metal layer having openings at said resistances topermit radiation to impinge upon the latter.